Compositions containing coal tar and a polysulfide polymer and pavement sealed therewith



COMPOSITIONS CONTAINING COAL TAR AND A POLYSULFIDE POLYMER AND PAVEMENTSEALED rnnnnwrrn Frederick P. Homing, No'rthville, Mich., assignor toAllied Materials Corporation,- Oklahoma City, Okla, a corporation ofDelaware No Drawing. Application August 19', 1958 Serial No. 755,865

12 Claims. 01. 94-18) This application is a continuation-in-part of myapplication Serial No. 581,373, filed April 30, 1956 now abandoned.

The invention relates to a new composition obtained from a mixture ofold ingredients and having new characteristics and properties making thecomposition useful for many purposes. One of the important uses for thenew composition is as a joint sealer for concrete pavements which aresubjected to hot blasts from jet engines. The composition of the presentinvention when used as a sealer-for pavements on air fields withstandsall deleterious effects caused by jet aircraft. Moreover, thecomposition may be produced at a reasonable cost and can be convenientlyand economically applied to the joints in a concrete pavement.

In preparing my new compositions I use as one essential ingredient, apolysulfide liquid polymer capable of being converted to a tough rubberyelastomer. I have discovered that coal tar, although theoreticallyincompatible with a polysulfide liquid polymer, can nevertheless bemixed with it to produce a composition having excellent properties as ajet-resistant sealer. My invention in its broader aspects is based on mydiscovery of a composition comprising a polysulfide liquid polymer andcoal tar which can be readily polymerized. My invention alsocontemplates compositions containing various ingredients in variousproportions as hereinafter more fully set forth.

The polysulfide liquid polymer used in my new composition is adimercaptan manufactured in liquid form and capable of being polymerizedby suitable curatives to a tough rubber. It is a poly-functionalmercaptan containing recurring disulfide linkages (SS). It is sometimesrepresented by the formula 1 Patrick and Ferguson, 2,466,963, April 12,1949 which also describes polysulfide liquid polymers which can be usedin the preparation of the compositions of the present invention.

Generally speaking the polysulfide liquid polymers which can be used inpreparing the compositions of the present invention are those having theformula:

where n is an integer from 3 to 108 or more and R is a radical of thetype disclosed in the said publication by 2,916,922 Patented Nov. 3,1959 2 Jorczak, et al. Usually the radical R can be represented by theformula Preferably a polysulfide liquid polymer is selected having theabove formula where n is from 10 to 70. The optimum range for n. is from20 to 45.

' Polysulfide liquid polymers having the above mentioned formula areavailable with varying amounts of tri-functionality and all appear to besuitable in the preparation of the compounds of the present invention.

As an example of one specific polysulfide liquid polymer there is acommercially available product having a viscosity about 400 poises at 25C. and a molecular weight about 4000. Its average structure is:

The coal tar used in my new composition is readily available as acommercial product and various grades can be used in carrying out myinvention. However, it has been found desirable to use coal tar having aviscosity within a range of 20 seconds Saybolt Furolat 77 F. to secondsSaybolt Purol viscosity at 210 F. The optimum range is 200 to 700seconds Saybolt Furol viscosity at 77 F. as tested by ASTMD88-44. It isalso possible to use a high viscosity coal tar or equivalent product ifits viscosity is reduced with an aromatic base lighter fraction and,again, my invention, in its broader aspec contemplates use in thecomposition of coal tars of lower viscosity also. However, it has beenfound that the loss ofthe volatile fraction upon aging of the finishedproduct has a deleterious effect on the performance of the polymerizedcomposition and therefore it is preferable to use a coal tar which willgive a final composition having properties that will remainsubstantially constant for many years.

In addition to the polymer and coal tar, I have found it desirable tointroduce an extender or filler, preferably of an inorganic nature.Although many of the materials frequently employed as fillers in rubberchemistry may be used for this purpose, I have found that the bestresults are obtained with so-called hard clay. This material not onlyacts as an extender but it reinforces the polymerized mass. Also, itimparts to the polymerized mass the highest resistance to the action ofthe blast from jet engines. It must be understood, however, that theinvention contemplates other fillers such as carbon black, various typesof clay fillers, slate flour, silica, limestone, calcium carbonate,asbestine, etc., when used as supplements to the polymer-coal tarmixture.

My invention does not reside in the discovery of any new curing agent,and the composition may include any substance which will condense withthe hydrogen of mercapto terminals and act as a curing agent. Thus ingeneral such products may be used as are set forth in the patent toPatrick et al., 2,466,963, column 30, lines 36 to 67. I have found leadperoxide to be satisfactory. instead of lead peroxide, one may use othermetallic oxides in the presence of hexamethylenetetramine or,alternatively, one may use organic peroxides such as benzoyl peroxide,tertiary butyl hydroperoxide, tertiary butyl perbenzoate and cumenehydroperoxide.

In carrying out my invention the curing agent must be introduced intothe mixture of polymer and coal tar at about the time the composition isapplied to the work, since polymerization is rapid and the mixturebecomes difficult to apply satisfactorily after a short time. To aid inobtaining a uniform distribution of catalyst throughout the mixture, itis preferably to make up two separate liquid components, the onecontaining all of the polymer and the other all of the curing agent. Theamount of the ingredients are chosen so that predetermined volumes ofthe two components when mixed together give a final composition of thedesired proportions. Preferably the proportions are such that when thetwo components are combined in equal volumes the desired finalcomposition is obtained.

The amount of curing agent used may vary in accordance with theknowledge of the art in connection with polysulfide liquid polymers, butI have found it desirable to use lead peroxide in amount about one-tenthby weight of the amount of polysulfide polymer used. Lecithin ispreferably added in minor amount for the purpose of reducing theviscosity, and minor amounts of accelerators, retarders andmiscellaneous fillers may also be present Without markedly changing thegeneral nature of the composition of my invention. Small amounts oforganic acids may be incorporated in the formulation to retard the rateof polymerization. Stearic acid in the amount of 1 to 4% of thepolysulfide liquid polymer has been found to be the most effective.However, the addition of retarders has been found to have an adverseeffect on the jet fuel resistance of the polymerized composition.

The following are specific examples of the invention:

Example 1 Two liquids are prepared, designated as components A and B,which when mixed in equal volumes result in the rapidly setting mixtureC. The proportions are:

In use, components A and B are mixed in equal volumes and the mixturequickly applied to the material to be sealed before it becomes tooviscous to handle, usually within one minute or less. Polymerizationstarts immediately upon mixing and is substantially complete within 48hours. The polymerized composition eifectively seals joints in concreteagainst the infiltration of moisture through repeated cycles ofexpansion and contraction. It is highly resistant to the deleteriouseffects of jet engine blast and jet fuel spillage.

In the above table the amounts of the ingredients are indicated inaccordance with a particular analysis and no range has been stated. Itmust of course be understood that the proportions can vary considerablyfrom the particular values set forth. The polysulfide liquid polymer isrelatively costly but is essential to the invention. It should bepresent to the extent of at least 10%, usually not less than 15%, anddesirably about 20% or more. There is no critical upper limit but thereis no appreciable advantage in employing more than 30% to 40% as anupper limit. The coal tar should be present in a ratio to the polymer atleast one to one, and often more, although a smaller ratio can be usedwhen the amount of polymer is increased toward the higher percentages.The optimum ratio of coal tar to polymer is two to one, at least from aneconomic standpoint. The range of coal tar in the final composition isdesirably between 25% and 60%, the optimum being about 40%. The clay orother filler can also be varied between and about 60%. In some cases itmay be desirable to use partly clay and partly other fillers.

Example 2 nent A 600 grams coal tar and 500 grams clay are mixedtogether in a mixer until the clay is thoroughly dispersed in the coaltar. Then 40 grams of lead dioxide is added and dispersed in the coaltar and clay. For component B 300 grams of clay is dispersed in amixture of 400 grams of polysulfide liquid polymer having a viscosity of300 poises and 200 grams coal tar. When component A is mixed in equalvolumes with component B a sealing composition is obtained ofapproximately 20% polysulfide liquid polymer, 40% coal tar and 40% clay.In order that this sealing composition may be effectively applied to ajoint to protect against intrusion of water and other foreign materialsit is usual to mix components A and B together through a mixing deviceand immediately extrude the mixture into the joint. The curing action israpid. Instead of using exactly equal volumes of the two components itis satisfactory to vary them to the extent of plus or minus 10% and evengreater differential in volumes may be satisfactory under somecircumstances.

Example 3 Component A is prepared by dispersing 20 grams lead dioxideand grams clay in 900 grams coal tar. Component B is prepared by mixing200 grams polysulfide liquid polymer having a viscosity of 1100 poiseswith 700 grams coal tar and then 100 grams clay is dis persed in themixture. Components A and B are then mixed in equal volume plus or minus10% through a mixer and immediately extruded into the joint. Uponmixing, the components immediately convert from a fluid product to atough rubbery solid capable of eifectively sealing joints againstintrusion of Water and other foreign materials. This sealing compositionis composed of approximately 10% polysulfide liquid polymer, 80% coaltar and 10% clay.

' Example 4 Component A consists of grams asbestine, grams lead dioxideand 800 grams coal tar. Component B consists of 50 grams asbestinedispersed in 1000 grams polysulfide liquid polymer having a viscosity of100 poises. When components A and B are mixed as in the precedingexamples a tough rubbery solid capable of effectively scaling isobtained. The sealing composition consists of about 50% polysulfideliquid polymer, 40% coal tar and 10% asbestine.

Example 5 In the same manner as the preceding examples a sealingcomposition can be obtained composed of about 30% polysulfide liquidpolymer, 40% coal tar and 30% slate flour. This composition is obtainedby mixing component A containing 400 grams slate flour, 60 grams leaddioxide and 700 grams coal tar with component B containing 200 gramsslate flour, 600 grams of polysulfide liquid polymer having a viscosityof 500 poises and 100 grams coal tar.

Example 6 Component A consists of 200 grams ground calcium carbonate, 40grams lead dioxide and 800 grams coal tar. Component B consists of 200grams ground calcium carbonate, 400 grams polysulfide liquid polymerhaving a viscosity of 400 poises and 400 grams coal tar. The sealingcomposition obtained by mixing the components in approximately equalvolume is composed of 20% polysulfide liquid polymer, 60% coal tar and20% calcium carbonate.

Example 7 Component A7 contains 50 grams lead dioxide and 1000 gramscoal tar. Component B contains 500 grams polysulfide liquid polymerhaving a viscosity of 350 poises and 500 grams coal tar. When the twocomponents are mixed in substantially equal volume a tough sealingcomposition is obtained composed of about 25% polysulfide liquid polymerand 75% coal tar.

It is to be understood that in the above examples it is within thepurview of the invention to substitute for the particular fillers listedany other type fillers and ex" tenders that are commonly used in therubber industry for equivalent purposes. It is also understood that thecuring agent need not be lead dioxide but any of the other curing agentsknown to be effective with the polysulfide liquid polymers as previouslyset forth.

It should also be noted that while the components listed above areblended in equal volumes a joint sealing composition can be prepared inaccordance with the present invention in which the proportion can be 2to 3% of component A and 97 to 98% of component B as long as the curingagent is in one component and the polysulfide liquid polymer is in theother component until the two components are mixed. For practicalpurposes it is simpler to prepare the separate components in suciproportions that the desired final composition will be obtained when thecomponents are mixed in substantially equal volumes.

It is to be understood that the composition of this invention is notonly useful for a sealer resistant to jet fuels but may also beadvantageously employed for other sealing purposes and as a quicksetting, non-thenno plastic composition for general use.

What I claim as my invention is:

l. A composition comprising at least about of a polysulfide liquidpolymer and coal tar, said polymer containing recurring disulfidelinkages (S-S--) and being a polyfunctional mercaptan.

2. A composition according to claim 1 in which the polymer has theformula where n is 3 to 200.

3. A composition according to claim 2 where n is 10 to 70.

4. A composition according to claim 2 where n is 20 to 45.

5. A composition according to claim 2 where n is about 24.

6. A composition according to claim 1 wherein the ingredients arecombined into two separate liquids, one of which contains said polymerand the other contains the curing agent for said polymer.

7. A composition according to claim 6, containing also up to 60% offiller.

8. A joint sealer for pavements comprising at least about 10% ofpolysulfide liquid polymer and coal tar, said polymer containingrecurring disulfide linkages (S-S) and being a polyfunctional mercaptan,said sealer being capable of effectively preventing the infiltration ofwater into the joints of said pavements and being adapted to withstandthe high temperatures due to jet engine blasts.

9. A polymerized solid mass comprising at least about 10% of polymerizedliquid polysulfide and coal tar, said polymer containing recurringdisulfide linkages (SS) and being a polyfunctional mercaptan, saidpolymerized mass being adapted to maintain joints in concrete pavementsin a sealed condition and to withstand temperatures due to jet engineblasts.

10. in a pavement, the combination of adjacent pavement portions capableof relative movement'under expansion and contraction, and a jointsealing composition between said portions comprising at least about 10%of polymerized liquid polysulfides, and coal tar, said polymercontaining recurring disulfide linkages (-SS-) and being apolyfunctional mercaptan.

11. A composition comprising by Weight 10% to 40% of polysulfide liquidpolymer, 25% to of coal tar and 25% to 60% of filler, said polymercontaining recurring disulfide linkages (-S-S) and being a polyfunctionmercap'tan.

12. A composition comprising at least about 10% of a polysulfide liquidpolymer and coal tar in a ratio to said polymer of at least two to one,said polysulfide polymer being a polyfunctional dimercaptan commerciallyavailable as a viscous liquid about 400 poises at 25 C. having amolecular weight about 4,000 and having a formula HS RSS RSH ReferencesCited in the file of this patent UNITED STATES PATENTS 2,169,814 PatrickAug. 15, 1939 2,282,948 Dietzel May 12, 1942 2,294,217 Tengler Aug. 25,1942 2,347,182 Coffman Apr. 25, 1944- OTHER REFERENCES Jorczak et al.:Polysulfide Liquid Polymers, Ind. Eng. Chem, volume 43, No. 2, February1951, page 325.

1. A COMPOSITION COMPRISING AT LEAST ABOUT 10% OF A POLYSULFIDE LIQUIDPOLYMER AND COAL TAR, SAID POLYMER CONTAINING RECURRING DISULIFEDLINKAGES (-S-S-) AND BEING A POLYFUNCTIONAL MERCAPTAN.